Fluid motor



Dec. 14, 1965 C. L. ENGLISH FLUID MOTOR Original Filed Feb. 13, 1961 570 TLC-T-J.

4 Sheets-Sheet 1 T .L E. 2

INVENTOR.

Dec. 14, 1965 c. ENGLISH 3,222,994

FLUID MOTOR Original Filed Feb. 13. 1961 4 Sheets-Sheet 2 INVENTOR. CHAPL as L. E'A/GL/SH f .1. E5 A rap/vars United States Patent 3,222,994 FLUID MOTOR Charles L. English, 2204 E. 25th Place, Tulsa, Okla. Original application Feb. 13, 1961, Ser. No. 89,053, new Patent No. 3,109,379, dated Nov. 5, 1963. Divided and this application Aug. 14, 1963, Ser. No. 305,913 7 laims. (Cl. 91-224) This application is a division of application, Serial No. 89,053, filed February 13, 1961, now Patent No. 3,109,379.

This invention relates generally to improvements in fluid motors for operating subsurface pumps utilized in oil Wells and the like, and more particularly but not by way of limitation, to reciprocating fluid operated motors.

Subsurface fluid operated pumps have been known in the oil producing industry for many years. A complete pump unit comprises a fluid motor and a reciprocating type pump connected in tandem relation and being of a size to be raised and lowered through a well bore. In the operation of such pump units, the power fluid (which is normally clean oil) is pumped under relatively high pressure downwardly to the fluid motor of the pump unit which provides a reciprocation of the motor and the pump. The pump draws in the well fluids and pumps the well fluids upwardly to the top of the well, usually along with power fluid exhausting from the motor or engine end of the unit. It may also be noted that such pump units may be either an insert type or a free type. An insert type of pump unit is suspended on the lower end on a string of relatively small diameter tubing through which power fluid is fed downwardly to the fluid motor. The pumped well fluids and exhausting power fluid are directed upwardly through a larger string of tubing or through the well casing in which the pump unit is seated. A free type pump unit is provided with suitable cups and is of a size such that the pump unit can be literally pumped upwardly and downwardly through one string of tubing into a pump cavity communicating with the tubing in which the pump is disposed and with a separate string of tubing. In operation of the free type of pump, the two strings of tubing are normally arranged side-by-side and power oil is forced down one of the tubings while the pumped well fluids and exhausting power fluid are directed upwardly through the other tubing.

Until recently, subsurface hydraulic or fluid operated pump units have been considered economically feasible in wells ranging from five thousand to ten thousand feet having what may be considered a rather moderate production, such as one hundred to two hundred barrels per day. Very few wells were drilled deeper than ten thousand feet and the production in relatively shallow wells in this country is usually relatively small, such as less than one hundred barrels per day. Most shallow Wells having limited production can normally be pumped more efliciently by means of a sucker rod type pump having a surface power unit. However, with the advent of deeper wells and with the advent of water flooding and similar operations, the potential for subsurface hydraulic pumps has been substantially increased. Subsurface hydraulic pumps may be used in these latter two conditions providing certain problems are solved in the construction of the pump units.

It is rather apparent that, assuming a given production, the deeper well, the more horsepower required for lifting the well fluids and exhausting power fluid to the top of the well. Furthermore, it is rather apparent that the diametrical dimensions of a hydraulic pump unit are limited by the diameter of the well in which the pump is to be used. One method of increasing the horsepower output of the engine end of a pump unit is to utilize a conventional fluid motor and merely increase the pressure of the power oil being fed to the motor. In theory, this 3,222,994 Patented Dec. 14, 1965 'ice solution appears to be very eflicient, since the minimum frictional losses arise through pumping a limited amount of oil at a high pressure. However, the pressure required at the well head for this type of method, such as 10,000 p.s.i. and even up to 20,000 p.s.i., becomes extremely dangerous. Special fittings and piping are required to handle the high pressure fluid, and a leak could easily kill workmen around the well head.

The use of water flooding and similar secondary recovery operations materially increases the production in the producing wells being used. These flooding operations may be used in formations of substantially any depth, but are presently being used mostly in relatively shallow formations. In any event, however, a subsurface hydraulic pump must have substantial capacity in order to provide the required production. Here again, it will be noted that the diametrical size of a pump unit is limited by the diameter of the well bore in which it is used. A double acting pump unit normally has a greater capacity than a single acting pump unit for a given diameter of pump cylinder. However, a double acting pump requires the use of two complete sets of valving and, in the diametrical limitations of most pump units, the valves must be extremely small which increases the cost of the pump unit and usually decreases the efliciency of the pump unit. Also, of course, the stroke length of a pump unit may be increased to increase the capacity, but this involves difficult alignment problems which will increase the cost of the pump unit. In addition to the foregoing, it hould be noted that the horsepower of a pump unit must be increased when the capacity of the pump unit is increased, and this is particularly apparent in the deeper wells.

The present invention contemplates novel fluid motors. The novel fluid motor of this invention contempl-ates'the use of a piston assembly having oppositely facing sets of working areas against which power fluid is applied for reciprocation of the piston assembly and wherein at least one set of the working areas has a total cross-sectional area larger than the cross sectional area of the interior of the cylinder in which the piston assembly reciprocates. The increased working faces of the piston assembly provide an increased horsepower output for the motor without the necessity of increasing the pressure of the power fluid. The quantity of power fluid required is increased, but this requirement is more than offset by being able to minimize the pressure requirements for the power fluid. The valve mechanism for the engine piston assembly may be located either in the piston assembly or in one head of the engine cylinder. In either event, a passageway is provided through the piston assembly from the valve chamber to supply and exhaust power fluid from one set of the working faces of the piston assembly to minimize the overall diameter of the motor and provide the most economic utilization of space. This construction of a fluid motor or engine is sometimes herein referred to as a complex engine end to distinguish it from a convention-a1 fluid motor having working areas on the piston no larger than the cross-sectional area of the motor cylinder.

An important object of this invention is to provide a subsurface fluid operated motor, which is operably connected with a subsurface pump, to efliciently and economically produce an oil well having substantially any production and horse power requirements.

Another object of this invention is to provide a novel fluid motor particularly adapted for a subsurface pump unit which will provide the maximum in horse power output with the minimum pressure requirements for power fluid utilized to operate the motor.

Another object of this invention is to provide a novel fluid motor having limited diametrical requirements and yet providing the maximum in working faces on the piston assembly of the motor.

A still further object of this invention is to provide a subsurface fluid operated motor which is simple in construction; is economical to manufacture, and will have a long service life.

Other objects and advantages of the invention'will be evident from the following detailed description, when read in conjunction with the accompanying drawings illustrating my invention.

In the drawings:

FIGURE 1 is a vertical sectional view through the upper portion of a pump unit utilizing a complex engine end.

FIGURE 1A is a horizontal cross-sectional view through the pump unit illustrated in FIG. 1 as taken along lines 1A1A of FIG. 1.

FIGURE 2 is a vertical sectional view of the lower portion of a pump unit and is a continuation from the lower end of FIG. 1.

FIGURE 3 is a schematic vertical sectional view through a pump unit of the type illustrated structurally in FIGS. 1, 1A and 2.

FIGURES 4 and 5 are schematic vertical sectional views through pump units having the same general combination of a complex engine and simple pump end as illustrated in FIGS. 1 through 3.

FIGURES 6, 7 and 8 comprise a vertical sectional view through a pump unit having both a complex engine end and complex pump end, with FIG. 6 being the upper portion of a pump unit, FIG. 7 being the central portion of the pump unit and FIG. 8 being the lower end of the pump unit.

FIGURE 9 is a schematic vertical sectional view through a pump unit of the type illustrated structurally in FIGS. 6, 7 and 8.

COMPLEX ENGINE END The pump unit 300 illustrated in FIGS. 1 and 2 is a free pump type of unit and generally comprises a complex engine 302 and a simple pump end 304 connected in tandem relation by a middle plug 306. The engine end 302 comprises upper and lower engine cylinder sections 308 and 310 interconnected by a tubular adapter 312 to contain the engine piston assembly generally designated by reference character 314 and which will be described in detail below. The lower end of the lower engine cylinder section 310 (FIG. 2) is threadedly connected to the upper end of the middle plug 306, and the upper end of the upper engine cylinder section 308 (FIG. 1) is closed by a cylinder head 316. A tubular adapter 318 is threadedly secured in a counterbore 320 in the upper end of the cylinder head 316 to support a downwardly facing swab cup 322 at the upper end of the pump unit. A

hollow nose cone 324 is threadedly secured at the upper end of the adapter 318 and is utilized to hold a retaining ring 326 downwardly against the swab cup 322 for securing the swab cup 322 in a fixed position on the adapter 318. A fishing neck 328 is formed on the upper end of the nose cone 324 to facilitate recovery of the pump unit 300 as will be readily understood by those skilled in the art. It will also be observed that ports 330 and 332 are formed in the nose cone 324 and the adapter 318 to allow the downward flow of high pressure power fluid through the nose cone and adapter assembly for a normal operation of the pump unit 300.

A downwardly facing valve seat 334 is formed in the tubular adapter 318 above the ports 332 and a valve head 336 is reciprocally disposed in the adapter 318 in a position to mate with the valve seat 334. A suitable spring 338 is seated in the counterbore 320 and constantly urges the valve head 336 upwardly toward the seat 334. Thus, the valve head 336 will be closed when no fluid pressure is acting downwardly across the valve head, such that any fluid pressure fluid acting upwardly through the ports 332 will be prevented from flowing through the nose cone 324 and will react across the downwardly facing swab cup 322 to facilitate the removal of the pump unit 300 from a well installation as a free pump. However, the valve head 336 will be moved downwardly against the action of the spring 338 when a downwardly directed pressure differential is exerted across the valve head to allow the flow of high pressure fluid downwardly through the nose cone 324 and then outwardly through the ports 332 for a normal pumping operation of the pump unit 300. The valve head 336 is guided and retained aligned with the valve seat 334 by means of a downwardly extending stern 340 sliding in a counterbore 342 in the head 316 and by a stern 344 sliding in a reduced diameter portion of the nose cone 324.

Ports 346 and 348 are formed in the lower end of the upper engine cylinder section 308 and in the upper end of the middle plug 306, respectively, to feed high pressure power fluid flowing downwardly through the nose cone 324 and adapter 318 around the pump unit 300 into the lower ends of the engine cylinder sections. Thus, during a normal operation of the pump unit 300, high pressure power fluid is constantly directed into the lower ends of the engine cylinder sections 308 and 310 for reciprocation of the engine piston assembly 314.

The engine piston assembly 314 comprises upper and lowerhollow piston heads 350 and 352 slidingly sealed in the respective cylinder sections 308 and 310 by suitable piston rings 354. A hollow rod 356 is threadedly secured in the lower end of the upper engine piston head 350 and extends downwardly through the tubular adapter 312. It will also be noted that the interior of the hollow rod 356 is in constant communication with the upper end of the upper engine cylinder section 308 above the upper piston head 350. Suitable packing 358 is secured in the adapter 312 by means of a retainer ring 360 threadedly secured in the upper end of the adapter to provide a sliding seal around the rod 356 and prevent the direct transfer of fluid between the lower end of the upper engine cylinder section 308 and the upper end of the lower engine cylinder section 310. The lower end of the hollow rod 356 is connected to the lower engine piston head 352 by tubular connector 362 to provide simultaneous reciprocation of the engine piston heads 350 and 352.

The valve mechanism generally designated by 364 is a three-way valve of the type illustrated in FIG. 1 of US. Patent No. 2,943,576 and generally comprises a pistontype valve 366 (FIG. 2) slidingly supported in a piston extension 368 between valve seats 370 and 372. The valve 366 has an extension 374 extending downwardly there from through the valve seat 372 which is contacted by a harness mechanism 376 for shifting the valve upwardly at the end of the downstroke of the engine piston assembly in the same manner as disclosed in the US. Patent No. 2,943,576. A restrictive diameter sleeve 378 (FIG. 1) is slidingly supported in the upper valve seat 370 for shifting the valve 366 downwardly at the end of the upstroke of the piston assembly in the same manner as in US. Patent No. 2,943,576. It will also be noted that the sleeve 378 is urged upwardly by a spring 380 to normally retain the sleeve 378 out of contact with the upper end of the valve 366.

A valve shifting mechanism 382 is carried in the tubular connector 362 above the engine piston head 352 for contacting the sleeve 378 and shifting the valve 366 downwardly at the end of the upstroke of the engine piston assembly, rather than by contact of the sleeve 378 with the upper end of the engine cylinder as in US. Patent No. 2,943,576. The valve shifting mechanism 382 comprises a head 384 slidingly secured in the tubular connector 362. as illustrated in FIGS. 1 and 1A. A pin 386 extends: through the head 384 and through slots 388 in opposite sides of the connector 362. The pins 386 extend out- Wardly from the connector 362 a suflicient distance to engage the lower end of the tubular adapter 312 near the end of the upstroke of the engine piston assembly. Therefore, the upward movement of the head 384 will be stopped prior to the end of the upstroke of the engine piston assembly to contact the upper end of the sleeve 378 and shift the valve 366 downwardly in substantially the same manner as illustrated and described in U.S. Patent No. 2,943,576.

The valve mechanism 364 controls the flow of fluid through a passageway 390 extending from ports 392 in the tubular connector 362 downwardly around the sleeve 378, the upper valve seat 370, the valve chamber of the valve member 366, through the lower valve seat 372 and around the chamber of the valve extension 374 to a chamber 393 at the lower end of the piston extension 368. The valve mechanism 364 also controls the flow of fluid through a second passageway 394 extending from the ports 392 upwardly into the tubular connector 362, then downwardly through the sleeve 378, the upper valve seat 370 and then through ports 396 which communicate with the valve chamber receiving the valve 366 and the engine cylinder section 310 below the engine piston head 352. It is not believed necessary to describe the detailed operation of the valve mechanism 364, since this operation is the same as that disclosed in US. Patent No. 2,943,576. It is believed suflicient to note that when the valve mechanism 364 is in its upper position as illustrated in FIGS. 1 and 2, power fluid standing in the engine cylinder section 310 above the lower piston head 352 is directed downwardly through the ports 392 and the passageway 390 to the exhaust chamber 393 while fluid is prevented from flowing upwardly through the passageway 394, such that high pressure power fluid is applied across the lower face of the piston head 352. In the opposite position of the valve mechanism 364, power fluid is prevented from flowing downwardly through the passageway 392 through the lower valve seat 372 and power fluid is directed upwardly through port 396 and the passageway 394 and ports 392 to act downwardly across the upper end of the piston head 352.

As shown in FIG. 2, a hollow connecting rod 398 is threadedly secured in the lower end of the engine piston extension 368 in communication with the exhaust chamber 393 and extends downwardly through the middle plug 306. Suitable packing 400 is held in the middle plug 306 around the rod 398 by a suitable retainer 402 to prevent the leakage of fluid between the engine cylinder section 310 and the pump end 304. The lower end of the hollow connecting rod 398 is threadedly secured to a hollow pump piston 404 having a traveling valve 406 therein. The traveling valve 406 is adapted to mate with a valve seat 408 threadedly secured in the lower end of the pump piston 404 and is held concentrically with respect to the seat 408 by a stem 410 extending through a guide 412 formed in the seat 408. A valve stop 414 is formed in the piston 404 a short distance above the traveling valve 406 to limit the opening movement of the traveling valve. A chamber 416 is formed above the stop 414 and communicates with the upper end of the pump piston 404 through ports 416 extending at an angle through the pump piston to the interior of the pump piston.

The pump piston 404 is slidingly sealed in a pump cylinder 418 by suitable piston rings 420 to provide a pumping action as will be described. The upper end of the pump cylinder 418 is secured to the middle plug 306 by a tubular adapter 422 having radial ports 424 therein which form exhaust ports for pumped well fluids and exhausting power fluid. The adapter 424 also functions to hold a seating ring 426 around the middle plug 306 against a retaining ring 428. The seating ring 426 is designed to engage the walls of a pump cavity (not shown) in which the pump unit 300 is positioned to separate high pressure fluid above the middle plug from the lower pressure below the middle plug.

A standing valve body 430 is threadedly secured to the lower end of the pump cylinder 418 and contains an upwardly facing valve seat 432 adapted to receive a standing valve 434. The valve 434 is retained concentrically with respect to the seat 432 by a stem 436 slidingly fitting in a tubular guide 438 formed in the valve seat. It will also be noted that upward movement of the valve 434 is limited by a suitable stop 440 formed in the upper end of the valve body 430. A seating shoe 442 is threadedly secured in the lower end of the valve body 430 to retain the valve seat 432 in operating position and to facilitate the seating of the pump unit 300 in a pump cavity. The shoe 442 also forms the well fluid inlet 444.

The overall operation of the pump unit 300 is best followed by reference to the schematic illustration in FIG. 3. As previously indicated, high pressure power fluid is constantly fed to the lower end of each of the engine cylinder sections 308 and 310 through the ports 346 and 348, respectively. With the three-way valve mechanism 364 in the position illustrated in FIG. 3, power fluid standing in the upper end of the upper engine cylinder section 308 above the engine piston head 350 is directed donwwardly through the hollow rod 356 and then outwardly through the slots 388 into the upper end of the lower engine cylinder section 310. This exhausting power fluid, along with the power fluid standing in the upper end of the cylinder section 310 is directed downwardly through the ports 392, the passageway 390 and the valve mechanism 364 into the hollow connecting rod 398. This power fluid is then further exhausted through the ports 416 in the upper end of the pump piston 404 into the upper end of the pump cylinder 418 for discharge through the ports 424. Thus, the upper face of each of the engine piston heads 350 and 352 is exposed to a pressure lower than the pressure of the power fluid directed through the ports 346 and 348, such that the engine piston assembly will be directed on an upstroke.

The pump piston 404 will obviously be moved onan upstroke simultaneously with the engine piston assembly to draw well fluids upwardly through the inlet 444 and around the standing valve 434 into the lower end of the pump cylinder 418. Simultaneously, fluid standing in the upper end of the pump cylinder 418, as well as the exhausting power fluid previously described, will be directed outwardly through the ports 424 into the production column. It will be apparent that the traveling valve 406 will be closed on the upstroke by reason of the downwardly acting pressure differential thereon.

Near the end of the upstroke of the pump unit 300, the valve shifting mechanism 382 contacts the tubular adapter 312 to initiate the shifting of the valve mechanism 364 to its opposite position where the valve mechanism provides communication between the passageways 394 and 390 and, in effect, closes off the upper end of the hollow connecting rod 398. In this latter position of the valve mechanism 364, high pressure power fluid being fed to the lower end of the engine cylinder section 310 is directed through the ports 396, passageway 394, valve mechanism 364, passageway 390 and ports 392 into the upper end of the cylinder 310 to act in a downward direction across the lower engine piston head 352. This power fluid is also directed through the slots 388 and upwardly through the connecting rod 356 into the upper end of the upper engine cylinder section 308 to act downwardly across the upper face of the upper engine piston head 350. As a result, both the upper and lower faces of each of the piston heads 350 and 352 are exposed to the action of high pressure power fluid. However, since the upper face of the upper engine piston 350 has an area larger than the exposed area of the lower face of the piston head 350, by reason of the hollow rod 356, the net hydraulic force on the engine piston assembly is in a downward direction to move the piston assembly on a downstroke.

On the downstroke of the pump piston 404, the standing valve 434 is closed and the traveling valve 406 is opened to provide a transfer of well fluids standing in the lower end of the cylinder 418 through the piston 404 to the upper end of the cylinder 418. It will also be noted that a volume of these well fluids equal to the volume occupied by the connecting rod 398 in the pump cylinder 418 will be forced through the ports 424 into the pro duction column to provide a minor production of fluid on the downstroke. However, since the major portion of the pumping action of the pump 302 takes place on the upstroke, the pump 304 is normally considered a single acting pump.

At the end of the downstroke of the pump unit 300 the valve mechanism 364 is shifted back to the position illustrated in FIG. 3 in the same manner as the shifting of the valve mechanism in US. Patent No. 2,943,576 to reverse the movement of the engine piston assembly and provide an upstroke.

In reviewing the construction and operation of the pump unit 300, it will be observed that the pump unit is a free-type pump unit comprising a complex engine end 302 and a simple pump end 304. This combination is particularly adapted for producing a well having normal production capacity but relatively high horsepower requirements. The engine piston assembly 314 provides two sets of working areas facing in opposite directions to provide a substantial increase in horsepower output compared with a simple engine end. The lower faces of the upper engine piston head 350 and the lower faces of the lower piston head 352 and piston extension 368 all obviously face in the same direction and have a combined area larger than the cross-sectional area of the engine cylinder sections 308 or 310. The upper ends of the upper piston head 350 and lower piston head 352 have still a larger combined area to provide a downstroke of the unit when both the upper and lower faces are exposed to the same high pressure fluid.

The pump unit 500 illustrated in FIG. 4 is provided herein to show an insert-type pump having the same general combination of a complex engine end and simple pump end. In fact, the pump end of the pump unit 500 may be the same construction as the pump end 304 of the pump unit 300 and is so illustrated in FIG. 4. The engine end 502 of the pump unit 500 comprises an engine cylinder 504 connected to the upper end of the pump cylinder 418 by means of a suitable middle plug 506 and having the same diameter as the pump cylinder 418. A suitable seating ring 508 is secured around the middle plug 506 to seat the pump unit 500 in a pump cavity as illustrated in US. Patent N 0. 2,917,000.

An engine piston assembly 510 is reciprocally disposed in the engine cylinder 504 and comprises vertically spaced heads 512 and 514 interconnected by a rod assembly 516. The upper piston head 512 is smaller in diameter than the lower piston head 514 and is reciprocally disposed in an insert 518 depending from the upper cylinder head 520. The lower end of the insert 518 is provided with a head portion 522 sealed by a packer 524 to the inner periphery of the engine cylinder 504 and sealed by a packer 526 around the rod assembly 16. It will also be noted that the insert 518 provides an annular passageway 528 communicating with the lower face of the piston head 512 through ports 530.

The rod assembly 516 provides an inner passageway 532 and an outer, annular passageway 534. The inner passageway 532 communicates through ports 536 with the upper end of the insert 518. Passageway 532 also communicates through a passageway 538 in the lower head 514 with the upper end of the piston head 514. Thus, the upper face of the upper engine piston head 512 and the upper face of the lower engine piston head 514 are in constant communication. The annular passageway 534 communicates with the low-er face of the upper piston head 512 through ports 540 and with the lower face of the lower piston head 514 through ports 542.

A three-way valve mechanism 544 of any suitable type, such as illustrated in FIG. 14 of US. Patent No. 2,943,576 is supported in the upper cylinder head 520 and actuated by the piston assembly 510 through a trip rod 546. The valve mechanism 544 is arranged for shifting at the upper and lower ends of the stroke of the pump unit 500 by contact of the trip rod 546 by the engine piston assembly 510 in a manner common to the art. An inlet passageway 548 extends through the cylinder head 520 into constant communication with the passageway 528 formed around the insert 518 and with one side of the valve chamber containing the valve mechanism 544. An outlet passageway 550 is also formed in the cylinder head 520 and extends from the valve mechanism 544 to the exterior of the pump unit. Another passageway'552 is formed in the cylinder head 520 between the valve mechanism 544 and the upper end of the insert 518 to control the flow of fluid to and from the upper faces of the engine piston heads, as will be described.

With the valve mechanism 544 in the position shown in FIG. 4, the upper face of the upper engine piston head 512 is exposed to exhaust fluid pressure through the passageway 552, valve mechanism 544 and exhaust passageway 550. Simultaneously, the upper face of the lower piston head 514 is also exposed to exhaust fluid pressure through passageway 538, passageway 532 and ports 536. At the same time, high pressure fluid is directed through the inlet 548, annular passageway 528 and ports 530 against the lower face of the upper engine head 512. This high pressure fluid is also directed through the ports 540, annular passageway 534 and port 542 against the lower face of the lower engine piston head 514. As a result, the engine piston assembly 510 is moved on an upstroke to raise the pump piston 404 and draw in a supply of well fluid around the standing valve 434 of the pump end 304.

Near the end of the upstroke of the pump unit 500, the engine piston assembly 510 contacts the trip rod 546 to shift the valve mechanism 544 in a direction to close the exhaust passageway 550 and open the passageway 552 to the inlet 548. The high pressure power fluid will then be directed through the valve mechanism 544 and the passageway 552 to react in a downward direction across the upper face of the upper engine piston head 512. This high pressure power fluid is also directed downwardly through the ports 536 and the passageways 532 and 538 to react across the upper face of the lower engine piston head 514. Therefore, both the upper and lower faces of both of the engine piston heads are exposed to high pressure fluid. However, since the combined areas of the upper faces of the piston heads 512 and 514 is larger than the combined areas of the lower faces of these piston heads, the piston assembly 510 will be moved on a downstroke. Well fluids standing in the lower end of the pump cylinder 418 will, therefore, be directed upwardly around the traveling valve 406 and through the ports 416 into the upper end of the pump cylinder. A portion of these well fluids will also be forced outwardly through the exhaust port 554 in the middle plug 506 into the production column. Near the end of the downstnoke of the pump unit 500, the engine piston assembly 510 again contacts the trip rod 546 to shift the valve mechanism 544 back to the position illustrated in FIG. 4 to reverse the movement of the engine piston assembly and provide an upstroke in the manner previously described.

In briefly reviewing the construction and operation of the complex engine and 502 of the pump unit 500, it will be observed that the lower faces of the piston heads 512 and 514 are in constant communication and have a combined cross-sectional area larger than the cross-sectional area of the engine cylinder 504 to provide a substantial power output on the upstroke of the pump unit. It will also be observed that the upper faces of the piston heads 512 and 514 have a combined area larger than the downwardly facing areas of these piston heads since no rod extends upwardly from the upper piston head 512. Therefore, the engine piston assembly 510 provides two sets of working areas facing in opposite directions and each set of working faces has a combined area larger than the cross-sectional area of the engine cylinder. The

9 three-way valve mechanism 544 alternately directs power fluid toward and away from the upper faces of the engine piston head to provide a reciprocation of the engine piston assembly 510 and operation of the pump end 304.

The pump unit 600 shown in FIG. is another illustration of a pump unit comprising a complex engine and 602 and a simple pump end, such as the pump end 304 illustrated in FIGS. 3 and 4 and previously described. The engine end 602 comprises an engine cylinder 604 connected in tandem relation with the pump cylinder 418 through use of a middle plug 506 of the same construction illustrated and described in FIG. 4. An engine piston assembly 606 is reciprocally disposed in the engine cylinder 604 and comprises what may be considered upper and lower heads 608 and 610 interconnected by a sleeve 612. The upper engine piston head 608 is an annular shaped member and is provided with a packer element 614 around the inner periphery thereof sealingly engaging an extension 616 extending downwardly into the engine cylinder 604 from the upper cylinder head 618.

The extension 616 is provided with an enlarged head portion 620 on the lower end thereof of a size to slidingly and sealingly engage the inner periphery of the sleeve 612 which interconnects the engine piston heads 608 and 610. The head 620 is positioned in the central portion of the engine cylinder 604 to allow the maximum travel of the engine piston assembly 606 in opposite directions. An annular passageway 622 extends through the extension 616 from the high pressure power fluid inlet 624 in the head 618 to ports 626 in the upper end portion of the extension head 620 to constantly direct high pressure power fluid into the annular space between the extension 616 and the engine piston assembly sleeve 612 underneath the engine piston head 608. It will also be noted that ports 628 are also provided in the upper end portion of the sleeve 612 immediately under the head 608 to direct this power fluid into the lower end portion of the engine cylinder 604 underneath the lower engine piston head 610. A central passageway 630 is formed through the extension 616 from ports 632 communicating with the lower face of the extension head 620. The upper end of the central passageway 630 communicates through a passageway 634 with the upper end of the engine cylinder 604 above the upper engine piston head 608.

A suitable three-way valve 636, such as the threeway valve illustrated in FIG. 1 in US. Patent No. 2,943,576, is carried by the lower engine piston head 610 to control the application of high pressure power fluid to the upper faces of the engine piston heads 610 and 608, as will be described. A port 638 extends from the lower face of the engine piston head 610 to the valve 636 and another port 640 extends from the upper face of the head 610 to the valve 636. A third port 642 associated with the valve 636 communicates with a hollow connecting rod 644 extending from the lower end of the piston 610 through the middle plug 506 into connection with the pump piston 404.

When the three-way valve 636 is positioned as illustrated in FIG. 5, the port 638 is closed and the ports 640 and 642 are placed in communication. Therefore, the high pressure power fluid being directed underneath the engine piston heads 608 and 610 will be prevented from flowing through the chamber containing the valve 636 and will therefore only react in an upward direction across the lower faces of the piston heads 608 and 610. The upper end of the engine cylinder 604 communicates with a lower pressure through the passageways 634 and 630 and the ports 632 with the interior of the sleeve 612 below the extension head 620. The latter chamber in turn communicates with lower pressure through the port 640, valve 636, port 642, hollow connecting rod 644 and ports 416 in the pump piston 404. Therefore, the high pressure power fluid acting against the lower faces of the engine piston heads 608 and 610 will move the engine piston 10 assembly 606 in an upstroke and the fluid standing in the engine cylinder 604 above the upper engine piston head 608 and the fluid standing in the extension 612 above the lower piston head 610 will be directed or exhausted into the production fluid column.

When the engine piston assembly 606 approaches the upper end of this stroke, the three-way valve 636 is shifted in the manner described in US. Patent No. 2,943,576 to provide communication between the ports 638 and 640 and to close the port 642. Therefore, high pressure fluid will flow from the lower end of the engine cylinder 604 through the ports 638, the valve 636 and the port 640 into the chamber directly above the lower engine piston head 610. This high pressure power fluid will continue to flow through the port 632 and passageways 630 and 634 into the upper end of the engine cylinder 604 to react in a downward direction on the upper face of the upper engine piston head 608. Careful inspection of FIG. 5 discloses that the exposed upper faces of the piston heads 608 and 610 has a combined area larger than the combined area of the exposed lower faces of the engine piston heads by an amount equal to the cross-sectional area of the hollow connecting rod 644, such that a net hydraulic force will be imposed in a downward direction on the engine piston assembly when all of these areas are exposed to the same fluid pressure. Therefore, the engine piston assembly 606 will be moved on a downstroke.

Near the end of the downstroke of the engine piston assembly 606, the three-way valve 636 is again shifted to the position illustrated in FIG. 5; whereupon, the upper faces of the engine piston heads 608 and 610 are again placed in communication with production column pressure to reverse the movement of the engine piston assembly and provide an upstroke.

In briefly reviewing the construction and operation of the pump unit 600, it will be apparent that the engine piston assembly of the pump unit provides two sets of working areas or faces extending in opposite directions. The combined area of each of these sets of working faces is larger than the cross-sectional area of the engine cylinder 604 to provide an increased horsepower output for the engine 602 compared with a simple engine construction. It will also be noted that the downwardly facing set of working faces has a combined area smaller than the combined area of the upwardly facing working faces and is continuously exposed to high pressure power fluid. The upwardly facing working faces are alternatively exposed to high and lower pressure fluid to provide the reciprocation of the pump unit.

COMBINATION COMPLEX ENGINE AND PUMP ENDS FIGS. 6, 7 and 8 structurally illustrate a pump unit 700 comprising a complex engine end 702 and a complex pump end 704. The engine end 702 generally comprises upper and lower cylinder sections 706 and 708 and upper and lower engine piston heads 710 and 712 reciprocally disposed in the respective cylinder sections and interconnected by a hollow rod 714 for simultaneous movement. The cylinder sections 706 and 708 are threadedly interconnected in tandem relation by a tubular adapter 716 having a packer element 718 therein for sealingly engaging the engine piston assembly and preventing direct communication between the two engine cylinder sections. The packing element 718 is retained in operating position by a suitable retainer nut 720. The upper cylinder head 722 at the upper end of the cylinder section 706 is tubular in form and is adapted at its upper end for connection with a tubing 724 extending from the top of the well in which the pump unit is disposed for directing high pressure power fluid into the pump unit.

The upper engine piston head 710 is provided with suitable piston rings 726 to slidingly seal the head in the cylinder section 706 and is tubular in form to provide a bore 728 extending vertically through the central portion thereof. A tube 730 is threadedly secured in the upper end of the bore 728 and extends upwardly through the cylinder head 722 to form an inlet for high pressure power fluid being fed to the pump unit. It will also be noted that a packer element 732 is secured in the cylinder head 722 around the tube 730, and the packer ele- .ment is held in operating position by a retainer nut 734. A port 736 extends transversely through the piston head 710 directly below the piston rings 726 to constantly direct high pressure power fluid against the lower face of the piston head 710, as will be more fully described. A chamber 738 is formed in the piston head 710 a short distance below the port 736 and communicates with the upper face of the piston head 710 through a vertical bore 740 extending alongside the central bore 728. The chamber 738 also communicates with a tube 742 secured in a counterbore at the lower end of the vertical bore 728 and extending downwardly through the packer element 718 of the adapter 716. The tube 742 terminates below the adapter 716 in open communication with the upper end of the engine cylinder section 708. Thus, the upper ends of the cylinder sections 706 and 708 are in constant communication through the bore 740, chamber 738 and tube 742.

As illustrated in both FIGS. 6 and 7, the hollow rod 714 interconnecting the engine piston heads 710 and 712 extends inside of the tube 742 and provides a continuation of the passageway formed by the bore 728 in the upper piston head 710. The lower end of the hollow rod 714 is connected to the upper end of the lower engine piston head 712 by means of a suitable adapted 744 and communicates with a chamber 746 formed directly under the adapter 744. The chamber 746 in turn communicates with a vertical bore 748 extending to the lower end of the engine piston 712 to provide continuous communication between the lower ends of the engine cylinder sections 706 and 708 through the port 736 and bore 728 in the upper engine piston 710, the hollow rod 714, the chamber 746 and the bore 748 in the lower piston head 712. Thus, the lower ends of both of these engine cylinder sections are constantly exposed to high pressure power fluid from the inlet tube 730. Suitable piston rings 750 are carried by the lower piston head 712 in sliding and sealing engagement with the cylinder section 708 in a manner common to the art.

A three-way valve mechanism, generally designated by reference character 752, is carried by the lower engine piston head 712 to control the flow of fluid from the lower end of the engine cylinder section 708 to the upper end of the engine cylinder section 708, as well as between the upper end of the cylinder section 708 and a hollow connecting rod 754 extending downwardly from the lower piston head 712 to the pump end 704. The valve mechanism 752 generally comprises a pair of vertically spaced va-lve seats 756 and 758 secured in the desired positions in a tubular extension 760 extending downwardly from the main body portion of the lower engine piston head 712 and a tubular valve 762 adapted to alternately seat on the seats 756 and 758. The valve mechanism 752 illustrated in FIG. 7 has the same construction and operation as the valve mechanism illustrated in FIGS. 16 and 17 of U.S. Patent No. 2,943,576. It is, therefore, believed necessary only to point out the main structural components in this specification. The upper valve seat 756 is secured at the lower end of the main body of the piston head 712 and extends into a bore 764 to form an anchor for a helical spring 766. A sleeve 768 extends loosely through the bore 764 and the valve seat 746 and is provided with a flange 770 near the upper end thereof to receive the upper end of the spring 766, such that the sleeve 768 is normally retained in its upper position with the flange 770 in contact with a flange 772 formed in the bore 764. Ports 774 are formed in the lower end portion of the sleeve 768 and a e alternately opened and closed by the upper end portion of the valve 762 as the valve 762 moves toward and away from the valve seat 756.

A harness mechanism 776 is carried at the upper end of the engine piston head 712 and is provided with a crossbar or arm 778 at the lower end thereof to contact the upper end of the valve sleeve 768 and shift the valve mechanism 752 at the upper end of the upstroke, as in U.S. Patent No. 2,943,576. The harness mechanism 776 is normally retained above the upper end of the sleeve 768 by a suitable spring 780 resting on the upper end of the piston head 712. It will also be noted that projections or feet 782 are formed on the upper end of the harness 776 radially outward from the tube 742 for contact with the adapter 716 near the end of the upstroke of the pump unit.

The lower valve seat 758 of the valve mechanism 752 is threadedly secured to the upper end of the hollow connecting rod 754 and is provided with an upwardly facing seating area 784 to receive the lower end of the valve sleeve 762 when the valve sleeve is in its lowermost position. The valve seat 758 is also provided with a projection 786 of a size to be received in the lower end of the valve sleeve 762 in the same manner as in U.S. Patent No. 2,943,576. An insert 788 is positioned in the piston extension 760 directly above the main body portion of the valve seat 758 to form a seal around the valve sleeve 762 and is counterbored at its lower end to form a chamber 790 around the valve seating area 784. Ports 792 are formed in the valve seat 758 below the seating area 784 to provide communication between the interior of the valve sleeve 762 and the upper end of the hollow connecting rod 754 when the valve sleeve is raised off of the seating area 784.

The lower end 794 of the piston extension 760 is tapered downwardly and inwardly and is provided with external threads for engagement by a lock nut 796 which presses the end portion 794 of the piston extension tightly around the outer periphery of the hollow connecting rod 754 and retains the mechanism in assembly. Another helical spring 798 is positioned around the nut 796 to constantly urge the lower harness mechanism 800 downwardly to an inoperative position. The lower harness 800 comprises a plurality of arms 802 extending alongside the outer surface of the piston extension 760 and having their lower ends curved inwardly to receive the spring 798. The upper ends of the arms 802 are connected by screws 804 to a tubular actuator 806 extending around the valve sleeve 762. The actuator 806 has outwardly extending guides 808 extending through slots 810 in the piston extension 760 which allow vertical movement of the harness assembly 800. The actuator 806 is of a size to move in and out of a counterbore 812 formed in the extension 760 immediately underneath the upper valve seat 756 to restrict the flow of fluid through the ports 774 and control shifting of the valve mechanism 752 at the end of the downstroke as in U.S. Patent No. 2,943,576.

When the valve mechanism 752 is in the position shown in FIG. 7, high pressure fluid flows from the lower end of the engine cylinder section 708 through the slots 810 in the piston extension 760, the ports 774 in the valve sleeve 768 and then upwardly through the valve sleeve 768 into the upper end of the engine cylinder section 708 to provide a downstroke of the pump unit, as will be more fully hereinafter described. Near the end of the downstroke, the lower harness mechanism 800 is retarded by a middle plug 814 (FIG. 8) at the lower end of the engine cylinder section 708 to move the actuator 806 into the counterbore 812 and shift the hydraulic forces acting on the valve mechanism 752, such that the valve member 762 is shifted upwardly onto the upper valve seat 756. The upper end of the engine cylinder section 708 is then placed in communication with the hollow connecting rod 754 through the valve sleeve 768, tubular valve 762, counterbore 790 and ports 792 in the lower valve seat 13 758 to provide an upstroke for the pump unit, as will be described. Near the end of the upsroke of the pump unit, the feet 782 of the upper harness 776 contact the lower end of the adapter 716 and retard further upward movement of the upper harness mechanism. The upper end of the valve sleeve 768 is then brought into contact with the harness arm 778 for downward movement of the sleeve 768 in the bore 764 of the piston head 712. This movement of the valve sleeve 768 shifts the valve mechanism 752 back to the position shown in FIG. 7 as explained in detail in US. Patent No. 2,943,576.

The pump end 704 illustrated in FIG. 8 comprises two cylinder sections 816 and 818 containing two pump piston heads 826 and 822, respectively. The upper pump cylinder section 816 is connected to the lower end of the lower engine cylinder section 708 by means of the middle plug 814 as previously mentioned. The middle plug 814 is tubular in form and contains a packer element 824 held in sealing relation around the hollow connecting rod 754 by a retainer nut 826. The middle plug 814 is also provided with ports 828 therein extending from a counterbore 830 in the lower end of the plug to the outer surface of the plug for discharge of pumped well fluids and exhausting power fluid to the exterior of the pump unit, as will be more fully described.

The lower pump cylinder section 818 is connected to the lower end of the upper pump cylinder section 816 by means of a tubular adapter 832 having a counterbore 834 in the lower end thereof. Ports 836 extend upwardly and outwardly through the adapter 832 from the upper end of the counterbore 834 for the discharge of pumped well fluids to the exterior of the pump unit, as also will be hereinafter described.

A standing valve body 840 is secured to the lower end of the lower pump cylinder section 818 to receive a standing valve 842. The valve 842 cooperates with a valve seat 844 secured in the valve body 840 by means of a tubular seating shoe 846. It will be noted that the standing valve 842 opens in an upward direction and closes in a downward direction for controlling the flow of well fluids through the well fluid inlet 848 formed by the seating shoe 846. A valve stem 850 depends from the valve 842 and is guided by a tubular guide 852 formed in the seat 844 to retain the valve concentric with the seat. Also, a suitable stop 854 is formed in the upper end of the valve body 840 to limit the upward, opening movement of the valve 842.

The upper and lower pump piston heads 820 and 822 are interconnected by a hollow rod 856 extending through the tubular adapter 832. A suitable packing element 858 is secured in the adapter 832 in sealing relation around the rod 856 by a retainer nut 860 to prevent direct communication between the upper and lower pump cylinder sections.

The upper pump piston head 820 is slidingly sealed in an insert 862 by suitable piston rings 864 to provide a pumping action upon reciprocation of the piston head 820, as will be described. The insert 862 is threaded at its upper end to the lower end of the middle plug 814 and is sealed at its lower end to the adapter 832 by a suitable sealing ring 866. Thus, the insert 862 forms an upper pumping chamber 868 between the lower face of the pump piston 820 and the upper end of the adapter 832.

A traveling valve 870 is positioned in a valve chamber 872 in the upper pump piston head 820. The traveling valve 870 is adapted to cooperate with an upwardly facing valve seat 874 secured in the lower end of the valve chamber 872 by an adapter 876 which is utilized to interconnect the piston head 820 with the hollow rod 856. It will also be noted that radial ports 878 are formed through the adapter 876 to provide communication between the pump chamber 868 and the valve chamber 872 and the upper end of the hollow rod 856. A valve stem 880 depends from the traveling valve 870 and is guided by a tubular guide 882 formed concentrically in thevalve seat 874 to maintain the traveling valve concentric with the valve seat. Ports 884 extend from the upper end of the valve chamber 872 upwardly and outwardly into communication with the upper end of the piston head 820 for the discharge of pumped well fluids therethrough, as will be hereinafter described. Also, a chamber 886 is formed in the upper end portion of the piston head 820 in a position to provide communication between the lower end of the hollow connecting rod 754 and the ports 884 for the discharge of exhausting power fluids into the upper end of the insert 862, as will also be hereinafter described.

The lower pump piston head 822 is provided with an auxiliary traveling valve 888 adapted to reciprocate in a valve chamber 890 extending from the central portion to the lower end of the respective piston head. The traveling valve 888 cooperates with an upwardly facing valve seat 892 which is retained in the valve chamber 890 by a retainer nut 894 to provide for an upward flow of fluids through the valve chamber 890 but to prevent a downward flow of fluids through this valve chamber. The valve stem 896 of the valve 888 is guided by a tubular guide 898 formed concentrically in the valve seat 892 to retain the valve concentric with the seat. A port 900 extends from the upper end of the valve chamber 890 to the upper face of the pump piston head 822 for the flow of pumped well fluids therethrough, as will be described. Also, a port 902 extends through the piston head 822 from the lower end of the hollow rod 856 to the lower end of the piston head 822 for the flow of well fluids from a lower pump chamber 904 between the lower piston head 822 and the standing valve 842, as will be described.

The overall operation of the pump unit 700 is best followed by reference to the schematic illustration of FIG. 9. High pressure power fluid is constantly fed through the tubing 724 extending from the top of the well to the pump unit 700. This high pressure power fluid flows downwardly through the tube 730 which forms an inlet for the pump unit. Power fluid from the tube 730 flows through the port 736 into the lower'end of the upper engine cylinder section 706 as well as flowing downwardly through the hollow rod 714 and the port 748 in the lower engine piston head 712 into the lower end of the lower engine cylinder section 708. Thus, the high pressure power fluid is constantly acting on the lower face of each of the engine piston heads 710 and 712 to constantly urge the engine piston assembly in an upward direction. With the valve mechanism 752 in the position illustrated in FIG. 9, the port 748 is closed with respect to the passageway formed by the sleeve 768 and this latter passageway is placed in communication with the port 792 to provide the same pressure in-the upper end of the lower engine cylinder section 708 and the hollow connecting rod 754. Since the hollow connecting rod 754 is in constant communication with production column fluid pressure through the port 884, the upper end of the insert 862 and the port 828, the upper end of the engine cylinder section 708 will likewise be at production column pressure when the valve mechanism 752 is in the position shown in FIG. 9. It will also be noted that the upper end of the upper engine cylinder section 706 is in communication with the same pressure through the port 740 and the tube 742 communicating at its lower end with the upper end of the engine cylinder section 708. Therefore, the upper faces of the engine pistons 710 and 712 will be exposed to a lower pressure than the lower faces of these pistons to provide an upstroke for the pump unit 700. During such an upstroke the fluid standing in the upper ends of the engine cylinder sections 706 and 708 will be exhausted downwardly through the various ports and passageways into the hollow connecting rod 754 and then will flow back upwardly through the ports 884, the upper end of the insert 862 and the ports 828 into the production fluid column.

At the end of the upstroke the valve mechanism 752 is shifted in the manner previously described and is disclosed in US. Patent No. 2,943,576; whereupon the port 748 is placed in communication with the passageway provided by the sleeve 768 and the port 792 is closed. The power fluid in the lower end of the engine cylinder section 708 will then be directed through the valve mechanism 752 and the sleeve 768 into the upper end of the cylinder section 708 to act in a downward direction on the upper face of the engine piston head 712. This power fluid will also flow on upwardly through the tube 742 and the port 740 into the upper end of the upper engine cylinder section 706 to act in a downward direction on the upper face of the upper engine piston head 710. In an operative pump unit structure, the tube 730 will have a smaller diameter than the hollow connecting rod 754, such that the combined areas of the upper faces of the pistons 710 and 712 will be larger than the combined area of the lower faces of these pistons. As a result, when all of these areas are subjected to power fluid pressure, a net hydraulic force will be directed in a downward direction to move the engine piston assembly on a downstroke.

At the end of the downstroke of the pump unit 700, the valve mechanism 752 is again shifted as previously described and as disclosed in US. Patent No. 2,943,576 to return to the position schematically illustrated in FIG. 9 and again provide an upstroke as previously described.

It will be apparent that the pump piston assembly com= prising the heads 820 and 822 and the hollow rod 856 will be reciprocated simultaneously with the engine piston assembly by virtue of the connection of the hollow connecting rod 754 between these two assemblies. On the upstroke of the pump piston assembly, any fluid standing in the upper end of the lower pump cylinder section 818 will be forced upwardly through the ports 836 into the production column. It will be apparent that the auxiliary traveling valve 888 will be held in a closed position during this stroke by virtue of a downwardly acting pressure differential thereacross. It will also be apparent that any fluid standing in the upper end of the insert 862 will be forced upwardly through the port 828 into the production fluid column since the traveling valve 870 will also be closed by virtue of a downward acting pressure differential. It will also be recalled that during this stroke of the pump unit 700, power fluid is exhausted from the engine end of the unit through the hollow connecting rod 754 to join with well fluids in the upper end of the insert 862 for discharge through the port 828.

Also on the upstroke of the pump piston assembly, well fluids are drawn in through the inlet 848 around the standing valve 842 into the lower pump chamber 904. It will further be apparent that a suction is created in the upper pump chamber 868 through the ports 878, rod 856 and port 902, such that the upper pump chamber 868 will be filled with well fluid simultaneously with the lower pump chamber 904. Both the main traveling valve 870 and the auxiliary traveling valve 888 are closed during such upstroke.

On the downstroke of the pump piston assembly, the standing valve 842 is closed and a portion of the well fluid standing in the lower pump chamber 904 is forced upwardly around the auxiliary traveling valve 888 and through the port 900 into the upper end of the lower pump cylinder section 818. The remainder of the well fluids in the lower pump chamber 904 is forced upwardly through the port 902 and hollow rod 856 to raise the main traveling valve 870; whereupon these well fluids are directed on upwardly through the port 884 into the upper end of the insert 862. Simultaneously, well fluids standing in the upper pump chamber 868 are forced through the port 878 and around the main traveling valve 870 for joinder with the well fluids flowing from the lower pump chamber 904. As a result, a rather small portion of the well fluid drawn into the pump unit on the upstroke will be discharged through the port 828 on the downstroke of the pump unit, such that the pump end 704 will be what is considered in the art a single acting pump. It should be noted, however, that during the downstroke of the pump piston assembly the upper face of each of the pump piston heads 820 and 822 is exposed to production column pressure, such that a minimum force is required for moving the pump piston assembly on a downstroke.

In reviewing the construction and operation of the pump unit 700, it will be observed that the engine piston assembly provides two sets of working faces facing in opposite directions, with each set of working faces having a combined area larger than a cross section of the engine cylinder. Therefore, the horsepower output ofthe complex engine 702 will be substantially greater than the horsepower output of a simple engine. The complex pump end 704 provides two pumping chambers which are simultaneously filled on the upstroke of the pump unit and exhausted on the downstroke of the pump unit. Since these pump chambers are filled only on the upstroke of the unit, the hollow connecting rod 754 will be subjected to a minimum of compression forces. Also, the action of production column pressure on the upper faces of both of the pump pistons on the downstroke further minimizes the compression forces required to be exerted through the hollow connecting rod 754. The pump end 704 requires a single standing valve and yet obtains a pumping capacity commensurate with the capacity of a double acting pump. The auxiliary traveling valve 888 may be of appreciable size as illustrated in FIG. 8 to minimize the cost of the structure.

From the foregoing it will be apparent that the present invention provides a novel subsurface fluid operated pump unit which will efllciently and economically produce an oil well having substantially any production and horsepower requirements. The complex engine of this invention provides the maximum working areas on the engine piston assembly for the diametrical size limitations to provide an increased horsepower output with a minimum increase in pressure requirements for the power fluid used for operating the engine. As a result, the power fluid can be maintained at a minimum pressure for a safe and economic well installation. It will further be apparent that the pump unit of this engine is simple in construction and will have a long service life.

Changes may be made in the combination or arrangement of parts or elements as heretofore set forth in this specification and shown in the drawings without departing from the spirit and scope of the invention as defined in the following claims.

I claim:

1. A subsurface pump unit fluid motor, comprising:

a cylinder member,

a piston member reciprocally disposed in the cylinder member,

said piston member having a first set of working areas facing one end of the cylinder member and a second set of working areas facing the opposite end of the cylinder member,

said first set of working areas having a combined area larger than the cross-sectional area of the interior of the cylinder member and larger than said second set of working areas,

said cylinder member having a power fluid inlet and an exhaust fluid outlet, a valve chamber in said piston member, first passageway means extending partially through the piston member from the valve chamber into communication with said first set of working areas,

second passageway means intersecting the valve chamber and communicating with both said inlet and said outlet,

valve means positioned in the valve chamber and operatively connected to the piston member for placing said first passageway means in communication with said inlet and applying power fluid pressure to said first set of working areas for one stroke of the piston member, and, alternately, placing said first passageway means in communication with said outlet during the opposite stroke of the piston member, and

means for applying fluid pressure against the second set of working areas during said opposite stroke of the piston member.

2. A motor as defined in claim 1 characterized further to include valve shift-ing means carried by the piston member for contacting the cylinder member at the ends of the strokes of the piston member and shifting the valve means to control the application of power fluid to said first set of working areas.

3. A fluid motor as defined in claim 2 characterized further to include a hollow connecting rod extending from the piston member through one end of the cylinder member, said hollow connecting rod forming said exhaust fluid outlet and a portion of said second passageway means.

4. A motor as defined in claim 3 characterized further to include another hollow rod extending from the piston member through the opposite end of the cylinder member, said last-mentioned hollow rod forming said power fluid inlet and a portion of said second passageway means.

5. A motor as defined in claim 1 wherein said lastmentioned means comprises passageway means extending from the power fluid inlet around said valve chamber into direct communication with said second set of work ing areas to constantly apply power fluid pressure against the second set of working areas.

6. A fluid motor as defined in claim 1 wherein said piston member comprises two spaced heads interconnected by a tubular section forming a portion of said first passageway means, said cylinder member having an inwardly extending packer therein slidingly sealed around said tubular section.

7. A fluid motor as defined in claim 1 wherein said cylinder member has a tubular extension on one end thereof extending partially through the cylinder member and forming a portion of said second passageway means, said piston member being in the form of a hollow member telescoped over and slidingly sealed around said tubular extension.

References Cited by the Examiner UNITED STATES PATENTS 208,449 9/ 1878 Winchester 91224 1,543,488 6/ 1925 Todd 10346 1,907,951 5/1933 Gage 91-313 2,156,537 5/ 1939 Mathews 91--320 2,718,880 9/1955 Deitrickson 91321 2,727,467 12/ 1955 Russell 91224 2,851,013 9/ 1958 Doughton 91224 2,943,576 7/1960 English 91-321 3,024,733 3/ 1962 English 10346 FRED E. ENGELTHALER, Primary Examiner. 

1. A SUBSURFACE PUMP UNIT FLUID MOTOR, COMPRISING: A CYLINDER MEMBER, A PISTON MEMBER RECIPROCALLY DISPOSED IN THE CYLINDER MEMBER, SAID PISTON MEMBER HAVING A FIRST SET OF WORKING AREAS FACING ONE END OF THE CYLINDER MEMBER AND A SECOND SET OF WORKING AREAS FACING THE OPPOSITE END OF THE CYLINDER MEMBER, SAID FIRST SET OF WORKING AREAS HAVING A COMBINED AREA LARGER THAN THE CROSS-SECTIONAL AREA OF THE INTERIOR OF THE CYLINDER MEMBER AND LARGER THAN SAID SECOND SET OF WORKING AREAS, SAID CYLINDER MEMBER HAVING A POWER FLUID INLET AND AND EXHAUST FLUID OUTLET, A VALVE CHAMBER IN SAID PISTON MEMBER, FIRST PASSAGEWAY MEANS EXTENDING PARTIALLY THROUGH THE PISTON MEMBER FROM THE VALVE CHAMBER INTO COMMUNICATION WITH SAID FIRST SET OF WORKING AREAS, SECOND PASSAGEWAY MEANS INTERSECTING THE VALVE CHAMBER AND COMMUNICATION WITH BOTH SAID INLET AND SAID OUTLET, VALVE MEANS POSITIONED IN THE VALVE CHAMBER AND OPERATIVELY CONNECTED TO THE PISTON MEMBER FOR PLACING SAID FIRST PASSAGEWAY MEANS IN COMMUNICATION WITH SAID INLET AND APPLYING POWER FLUID PRESSURE TO SAID FIRST SET OF WORKING AREAS FOR ONE STROKE OF THE PISTON MEMBER, AND, ALTERNATELY, PLACING SAID FIRST PASSAGEWAY MEANS IN COMMUNICATION WITH SAID OUTLET DURING THE OPPOSITE STROKE OF THE PISTON MEMBER, AND MEANS FOR APPLYING FLUID PRESSURE AGAINST THE SECOND SET OF WORKING AREAS DURING SAID OPPOSITE STROKE OF THE PISTON MEMBER. 